Perineural invasion (PNI) is a common feature of pancreatic ductal adenocarcinoma (PDAC).Here, we investigated the effect of PNI on the microenvironment and how this affects PDAC progression. Transcriptome expression profiles of PDAC tissues with different PNI status were compared, and the intratumoral T cell density and levels of neurotransmitters in these tissues were assessed. PNI was associated with impaired immune responses characterized by decreased CD8+ T and Th1 cells, and increased Th2 cells. Acetylcholine levels were elevated in severe PNI.Acetylcholine impaired the ability of PDAC cells to recruit CD8+ T cells via HDAC1-mediated suppression of CCL5. Moreover, acetylcholine directly inhibited IFN-γ production by CD8+ T cells in a dose-dependent manner, and favored Th2 over Th1 differentiation. Furthermore, hyperactivation of cholinergic signaling enhanced tumor growth by suppressing the intratumoral T cell response in an orthotopic PDAC model. Conversely, blockingResearch.

Background and aimsPancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related death worldwide. Neurotransmitter-initiated signalling pathway is profoundly implicated in tumour initiation and progression. Here, we investigated whether dysregulated neurotransmitter receptors play a role during pancreatic tumourigenesis.MethodsThe Cancer Genome Atlas and Gene Expression Omnibus datasets were used to identify differentially expressed neurotransmitter receptors. The expression pattern of gamma-aminobutyric acid type A receptor pi subunit (GABRP) in human and mouse PDAC tissues and cells was studied by immunohistochemistry and western blot analysis. The in vivo implications of GABRP in PDAC were tested by subcutaneous xenograft model and lung metastasis model. Bioinformatics analysis, transwell experiment and orthotopic xenograft model were used to identify the in vitro and in vivo effects of GABRP on macrophages in PDAC. ELISA, co-immunoprecipitation, proximity ligation assay, electrophysiology, promoter luciferase activity and quantitative real-time PCR analyses were used to identify molecular mechanism.ResultsGABRP expression was remarkably increased in PDAC tissues and associated with poor prognosis, contributed to tumour growth and metastasis. GABRP was correlated with macrophage infiltration in PDAC and pharmacological deletion of macrophages largely abrogated the oncogenic functions of GABRP in PDAC. Mechanistically, GABRP interacted with KCNN4 to induce Ca2+ entry, which leads to activation of nuclear factor κB signalling and ultimately facilitates macrophage infiltration by inducing CXCL5 and CCL20 expression.ConclusionsOverexpressed GABRP exhibits an immunomodulatory role in PDAC in a neurotransmitter-independent manner. Targeting GABRP or its interaction partner KCNN4 may be an effective therapeutic strategy for PDAC.